1. The Field of the Invention
The present invention is related generally to the field of medical catheters. More specifically, the present invention relates to a multiple sheath catheter for use in placing an intravenous (IV) catheter or other medical instrument into a blood vessel of a patient.
2. Technical Background
During medical treatment, patients often require medication, blood, or fluids. The most efficient way of administering these substances is by depositing them directly into the patient's blood stream where the circulatory system quickly directs the substance to the target tissue or organ. Thus, vascular catheters for infusion of fluids, blood, and medications into patients are among the most commonly used medical devices. The insertion of a vascular catheter allows repeated or continuous access to the circulatory system of a patient. Vascular catheters are generally inserted into the extremities of a patient and fluids, blood, and medications are provided to the patient through such catheters.
Catheters of this type are generally inserted into a vein or artery by means of an introducer needle. In one common configuration, the catheter is initially placed over the needle. The needle, with the catheter located over the needle, is inserted into the patient until the desired vein or artery is located. Once the needle and catheter are properly located in the vein or artery, the needle is withdrawn from the catheter and discarded. The catheter remains in the vein or artery to provide access to the circulatory system of the patient without repeated needle punctures.
When the catheter insertion and placement steps have been concluded, one end of a tube (or "tubing set") is generally attached to the proximal end of the catheter. The opposite end of the tube is attached to a source of fluid and medication. The source of fluid is typically a bottle or bag containing the fluid required for treatment of the patient. Once attachment of the catheter to the fluid source is completed, fluids are allowed to flow through the tubing, into the catheter, and ultimately into the patient. In most situations, fluids flow through the tubing set and into the patient by means of gravity feed or using a standard infusion pump.
It will be appreciated that it is important to minimize the risk of failure when introducing an IV catheter or other medical instrument into the blood vessel of a patient. Successful introduction of an IV catheter or other medical instrument into the blood vessel of a patient requires proper positioning of the tip of the needle within the blood vessel. Introduction may fail because the needle misses the blood vessel, partially impales the blood vessel, or "blows out" the blood vessel by penetrating the opposite wall after vascular access has been achieved.
Failure is especially likely when introducing IV catheters into the veins and arteries of geriatric patients, as such patients' blood vessel walls are generally less resilient than the blood vessel walls of younger patients. As a result, a medical professional introducing an IV catheter or other medical instrument into the vein of a geriatric patient may "blow out" the vein by inadvertently penetrating the opposite wall. Failure is also likely when introducing IV catheters into the veins and arteries of neonatal patients. Such patients have small diameter blood vessels which are hard to successfully penetrate unless the medical professional uses a small diameter needle to gain venous access.
It will also be appreciated that a medical professional may wish to place an IV catheter or introducer into a blood vessel that has the same size inside diameter as the outside diameter of the catheter or introducer. However, the failure modes described above are more likely to occur where the placement of the IV catheter or introducer requires the use of a large diameter needle.
It will be further appreciated that it is important to minimize the risk of infection when introducing an IV catheter or other medical instrument into the blood vessel of a patient. The method of insertion and placement of a catheter described above involves handling of the catheter by the medical professional. Such handling creates the potential for contaminating the catheter with microorganisms, allowing the introduction of such microorganisms into the patient's circulatory system.
Attempts have been made to deal with the problems that occur when introducing an IV catheter or other medical instrument into a blood vessel. However, the proposed solutions often involve the use of large diameter needles, which, compared to smaller diameter needles, cause greater tissue damage and increase the risk of failure. Such solutions also typically involve multiple steps, including the placement of a guide wire. Procedures involving multiple steps increase both the probability of error and the danger of infection. Moreover, such solutions typically involve numerous separate components, including a needle, guide wire, and vessel dilator. The use of multiple separate components renders such solutions cumbersome. In addition, the introduction of each new component into a patient's blood vessel increases the patient's risk of infection.
In one method known as the modified Seldinger technique, a hollow thin-walled needle is inserted into the blood vessel of a patient, creating an access site, after which a guide wire is introduced through the needle. The lumen of the needle must have a large enough inside diameter such that a guide wire can be introduced through it. The needle is then removed, and a vessel dilator such as a plastic cannula is threaded into the blood vessel over the guide wire. The guide wire is removed, after which an IV catheter or other medical instrument may be inserted through the cannula and into the blood vessel. In this technique, the needle, guide wire, and vessel dilator are separate components, making this technique cumbersome. In addition, the introduction of each new component-first the needle, then the guide wire, then the cannula-into a patient's blood vessel increases the risk of failure or infection.
In a variation of this technique, a guide wire is inserted into the patient's blood vessel as described above. A tear-apart or peelable sheath cannula is then inserted into the patient's blood vessel over the guide wire. After insertion of the IV catheter or medical instrument through the lumen of the cannula, the tear-apart or peelable sheath cannula is withdrawn from the blood vessel. The cannula is then split or peeled lengthwise, allowing the user to remove it from the inserted IV catheter or medical instrument. The cannula may also include a dilator disposed within the lumen of the cannula such that the distal end of the dilator extends beyond the distal end of the cannula, allowing dilation of the access site. The dilator and cannula are inserted into the patient's blood vessel over the guide wire, after which the guide wire is removed. The dilator may be removed by withdrawing it from the access site through the cannula, after which the IV catheter or medical instrument may be inserted into the patient's blood vessel.
Another technique involves the insertion of a tear-apart or peelable sheath cannula placed over an introducer needle. The needle, with the tear-apart cannula located over the needle, is inserted into a blood vessel of a patient. The needle is then withdrawn from the tear-apart cannula and a catheter may be inserted into the patient's blood vessel through the lumen of the tear-apart cannula. However, the outer diameter of the inserted catheter can be no larger than the outer diameter of the introducer needle used.
From the foregoing, it will be appreciated that it would be an advancement in the art to provide a device that would allow a user to gain access to a patient's blood vessel without using a large diameter needle. It would also be an advancement in the art to provide such a device which would allow dilation of the access site. It would be yet another advancement to provide a device that was easy to use and that did not require the use of multiple separate components. Finally, it would be a significant advancement in the art to provide such a device which decreased the risk of infection associated with the placement and use of a catheter.
Such apparatus are disclosed and claimed herein.